壁

Bottom earth radical - three strokes picturing a mound rising from a horizontal line. It indexes 壁 in the earthworks family because ancient walls were rammed earth, not stone. Same family: 城 city wall, 墙 wall, 堤 dyke, 基 foundation. The radical position at the bottom mirrors the way an earthen wall sits on the ground.

Top 辟 supplies the sound: pì → bì with a clean voicing shift. The same phonetic powers 避 avoid, 僻 remote, 譬 illustrate, 臂 arm. 辟 originally pictured a kneeling figure beside a knife and a mouth - a ruler issuing judgement, which generalized to 'to open up, to divide.' A wall is precisely what 'opens up' and divides space.